>For those that know something about sound, I have always wondered from what point sound measurements are made? During my engineering days I was responsible for many things including The Measurement of Sound, according to International Standards. Are such measurements as referred to in the media in the middle of the “pit” or two miles away? :)

I am not sure, but I wanted to comment that the whole issue of "decibels" is quite confusing, and the word "decibels" means at least three different things. You probably know most or all of the following already:

First of all, officially, decibels is simply the ratio of two power levels, expressed logarithmically (an increase of 10 decibels representing a 10-fold increase in power).

Presented like this, "decibels" as an absolute power level doesn't make sense - unless you define some arbitrary power level as zero decibels. Several such definitions can be, and have been, done. I am not sure what standard power level is used for sound.

Finally, once this definition has been made, and you want to apply it to sound, you can use decibels to represent the absolute amount of power produced by a sound source (which can be expressed in watts, and then converted to decibels), or to the intensity of the sound power that passes through an observer. In the latter case, decibels no longer represents watts, but watts per square meter (which means that yet another arbitrary "zero level" has to be defined).

It is the latter that is of obvious interest to concert halls. I suspect the ruling means that "no spectator or worker, whether at the front end or the back end of the hall, should be subject to more than so-and-so-much watts per square meter" (converted to decibels, of course).